Estimation of First-Flush Diverter Phenomena through Volume Based Grab sampling of Rainwater

M. ZAHIR, A. NAZ, T. AHMED, M. AHMAD

Abstract

The first-flush diversion is deliberately branded as a constructive intervention to cut both suspended and dissolved contaminants load in rainwater systems. Setting-up a first flush diverter (FFD) is an economical practice for enhancing the quality of harvested rainwater. This study depicts the estimation of the volume of first flush and quality of rainwater harvesting in Nathiagali, Abbottabad through volume based grab sampling of rainwater straight from the catchments area (roof) and contains analysis of few physicochemical water quality parameters including turbidity, pH, electrical conductivity (EC) and total dissolved solids (TDS). First flush phenomena distinct sediments, bird droppings, spiders, insects, mosquito eggs and debris from penetrating into the storage tanks. It depends on the preliminary rain to wash the roof beforehand water is stored in the main tank. Though there is almost widespread acceptance that this practice is valuable hence there is no stringent standards or agreements on how much water is to be diverted in the first flush as literature demonstrated fluctuated values. It depends on subsequent factors that affect the first flush including rainfall intensity or average rainfall, roof size, roof material, slope, exposure, antecedent dry time. This study recommended that, firstly, 25 to 30 gallons of rainwater should be diverted to the first flush.